speed1
New member
I was thinking of taking off the Muffler from the 6.5 hp . HF engine...Will that improve performance, will it hurt the engine or will I just be annoying my neighbors ? Thank you ...Bob
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r_chez_08
Should be in the shop...
Take off the muffler and make a straight pipe (or buy one)
Install a silencer if it is too loud.
Install a silencer if it is too loud.
klicky96
New member
I know someone is gonna make a comment on this post about back-pressure. So lets just throw it out there and say right now that a 4-stroke does not need back pressure haha.
exenos
Project Nut
2 strokes don't even need back-pressure. Its amazing the amount of people that don't realize that the pressure in a 2 stroke pipe is coming from the properly timed sound waves and not from pressure build up.
As for removing the muffler, yes just make a header with a pipe on it, i find that the longer the better (within reason) I have a 75cm (2.5 foot) pipe on my minibike and it does a great job of muffling the sound, just make sure that the extra weight is supported properly.
EDIT: dam just re-read the top half of my post about back pressure and realized that it could be taken the wrong way. No insult is intended to any one.
r_chez_08
Should be in the shop...
Yeah. There are hundreds of different exhausts available to buy for this motor. However, if we are making one, without a dyno, the safest bet is to make the pipe straight with no nasty joints etc.
Doc Sprocket
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If I've said this once, I've said it a million times. Back pressure is BAD. YOU try breathing out through a straw while exercising! Too many people confuse the terms "back pressure" and "cylinder scavenging".
Speed1- You MAY find your engine runs a little wonky after changing exhausts. This indicates that you need to adjust your mixture, and is normal.
speed1
New member
How do I adjust the mixture ? As far as mechanics I know how to put gas in the engine and change the oil , anything else would be like talking chinese to me 
Doc Sprocket
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Bing tao bang seng shin.
Oh, sorry. Jetting. You'd have to alter your main jet, or replace it with one of a different size. Older, non-emissions have adjustable needle jets, in which case, you just turn the screw.
Oh, sorry. Jetting. You'd have to alter your main jet, or replace it with one of a different size. Older, non-emissions have adjustable needle jets, in which case, you just turn the screw.
speed1
New member
Toystory, this is a newer 6.5hp , HF engine , does that mean I have to replace the main jet , what size, where is it located , where do I buy it? tao bom cun chau bin wong dong phu
souperman000
New member
I am actually learning chinese in school right now...and you guys suck! 
Doc Sprocket
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I am actually learning chinese in school right now...and you guys suck!
Yeah... Good!:toetap05:
Anyways, back on topic. See the big bolt at the bottom of the carb that holds the bowl on? Unscrew it and remove the bowl. You'll see a hollow tube that runs right up the middle of the carb. Insert a small flathead screwdriver into the tube, and you will be able to uscrew and remove the jet. Sizing depends on what your engine needs (if anything) after the change.
To determine if you need to rejet- warm up the engine to operating temp, shut 'er down, and remove the spark plug. Clean it up nice (or better yet install a brand new one). Put the plug back in, fire it up, and drive at full throttle up to top speed. Hold it at full throttle for a minute, and hit the kill switch to shut it down while still running full bore.
Remove the plug and look at it. If the ceramic insulator is bone white, you're running too lean and need the next larger jet. If it's a nice tan colour, your mixture is fine. If it's black, you're running too rich and need a smaller jet.
speed1
New member
ok, thanks toystory I will have my son try that tomorrow...Our chinese isn't that bad is it?
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